885 sec e 9

It's true that 'between' can be followed by plurals, eg:

▶BETWEEN PEOPLE/COUNTRIES◀

relations [plural]

a) official connections between countries, companies, organizations etc

Relations between the two countries have improved recently.

however, ETS doesn't seem to like the idea.     eg:

1.                            
Dr. Sayre’s lecture recounted
several little-known episodes in the relations between nations that
illustrates what is wrong with alliances and treaties that do not have
popular support.

(A) relations
between nations that illustrates

(B) relation of one
nation with another that illustrates

(C) relations
between nations that illustrate

(D) relation of
one nation with another and illustrate（B）

(E) relations of
nations that illustrates

so just remember     ETS' rule. no other way

这题好像还是没有定论!

请各位大侠继续讨论，为什么选D？而不选A？

between在这里为什么不对？

Between 虽然可以用于复数名词, 但强调的是任意两者之间比较.  betweeen boys and girls. 实际还是两个概念在进行比较,所以我认为这题A还是表达错误的.

这句里的take 做 require 解.   

E使原句变成了对灵活的平衡技巧的解释, 但这种技巧并非一定带来to..., 原句中技巧只是必要条件, E中成了充分条件了.